This thesis develops a technique for the identification, classification and quantification of instream flow environments. These features have been traditionally referred to as 'habitats' by lotic ecologists, in this research they are termed 'hydraulic biotopes'. The hydraulic biotope is the lowest of six nested levels of a hierarchical geomorphological model. This model has been developed as a tool to assist river managers, researchers and conservationists to categorise or classify rivers with respect to their geomorphic characteristics. Each level of the model provides data at a different level of resolution. This ranges from the broad scale catchment data to the site specific 'habitat' or hydraulic biotope data. Although this thesis is primarily concerned with the development of the hydraulic biotope, the interaction of all catchment variables needs to be recognised. Detailed analysis of hydraulic biotope data in the Buffalo River are presented within the broader hierarchical model. Consultation with lotic ecologists, together with a review of ecological literature, emphasised the need for a standardised terminology for the classification of ecologically significant instream flow environments. At present a fairly haphazard 'habitat' classification tends to be carried out by most researchers, this often leads to confusion in the identification and naming of different hydraulic biotopes ('habitats'). This confusion is exaggerated by the sharing of terminology between lotic ecology and fluvial geomorphology, usually for the categorisation of different types of features. A review of the ecological literature emphasises the importance of flow hydraulics within a river to describe the distribution of biota. The hydraulic variables considered to be most significant include velocity and depth. As river morphology directly determines the prevailing distribution of depth, velocity and substratum, it is obvious that there are important links to be made between fluvial geomorphology and lotic ecology. This thesis explores the potential of the hydraulic biotope as a tool to help develop those links. This thesis presents a standardised classification matrix for the identification of hydraulic biotopes. The matrix is simply based on water surface characteristics together with channel bed substratum. The validity of this matrix is tested by statistical analysis of hydraulic variables quantifying flow conditions within the various hydraulic biotope classes. Data is presented from four different river systems, each representing a different sedimentological environment. Where possible the influence of discharge has been considered. Results from more than 3000 data points show that hydraulic biotopes have distinct hydraulic characteristics in terms of velocity-depth ratio, Froude number, Reynolds number, 'roughness' Reynolds number and shear velocity. These hydraulic indices represent flow conditions both as an average within the water column, and near the bed. Statistical analysis shows that the hydraulic characteristics of the various hydraulic biotope classes are relatively consistent both within different fluvial environments and at different stages of flow. Unlike the morphological unit in which the hydraulic biotope is nested, in stream flow environments are shown to be temporally dynamic. Using the classification matrix as a tool for identification, hydraulic biotopes identified at one discharge are shown to be transformed from one class to another as a response to change in stage. The pattern of transformation is shown to be consistent within different sedimentological environments. An examination of the associations between hydraulic biotopes and morphological units demonstrates that, although some hydraulic biotopes are common to all morphological units (backwater pools, pools and runs), some features have specific associations. In this study rapids were found to be prevalent in bedrock pavement, bedrock pool and plane bed morphology, while cascades, chutes and riffles were common to plane bed, step and riffle morphology. Results from this research indicate that the hydraulic biotope, within the hierarchical geomorphological model, has the potential to aid the prediction of channel adjustment and associated 'habitat' (hydraulic biotope) transformation in response to changes in flow and sediment yield. These are likely to become increasingly important issues as South Africa strives to maintain a balance between the development of water resources to meet the needs of the rapidly expanding population, whilst at the same time maintaining the fluvial environment for sustainable use.

M.Sc. / The Lesotho Highlands Water Project (LHWP) is bound to adversely affect the ecology of the Orange River system and in particular the highland tributaries. The Senqunyane River (a tributary of the Orange River) would be no exception. Water extraction by means of the proposed Mohale Dam (Phase 1B of LHWP) is expected to alter the downstream habitat of the Senqunyane River, which is alarming as the rare rock catfish (Austroglanis sclateri) occur in these waters. Another concern is the lack of knowledge on the riverine ecology as no research has been conducted in the Senqunyane River downstream from the proposed Mohale Dam wall. In order to gain baseline information on the aquatic habitat, distribution and composition of the fish community as well as habitat parameters of the rock catfish , four surveys (from Spring 1994 to Summer 1996) were conducted in the Senqunyane River, major tributaries and in the Senqu River. This information is needed for future monitoring of downstream alterations to the riverine ecosystem and to determine the habitat preference of A. sclateri. Water quality variables were generally in accordance with the guidelines of Kempster, Hattingh & Van Vliet (1980) and the Department of Water Affairs and Forestry (1993), but excessive levels of un-ionized ammonia and phosphates were recorded at antropogenically disturbed areas. Two distinctly different fish communities were respectively found upstream and downstream from the Semongkoaneng Waterfall as this waterfall serves as a migration barrier. The upstream community consists entirely of Psemlobarbus quathlantbae (Maloti minnow), while the downstream community consists of Barb us amens (Smallmouth yellowfish). Labe() capensis (Orange River mudfish). Austraglanis .cclateri (rock catfish) and Oncorhunchus An ecological investigation of the aquatic vertebrates below the proposed Mohale Darn Wall in the Senqunyane River, Lesotho, with emphasis on the rock catfish (Austroglanis sclateri) al1111111Hry mykiss (Rainbow trout). B. aeneus has the highest-representation within this community while 0. mykiss has the lowest representation. Low numbers of the latter species is probably related to the temperature regime and bottom siltation and therefore the Senqunyane River can be regarded as of a marginal area for the occurrence of trout. A. sclateri also has a low representation within the community which is probably a result of its specific habitat requirements as apposed to 13. aeneus and L. capensis which utilize a wider variety of habitat types. Distinctly different habitat preferences were observed for different A. sclateri lifestages. Recruits preferred backwater pools, juveniles preferred suckles and adults preferred runs. It is clear that juveniles and adults prefer strong current velocities and would probably not do well in conditions of reduced flow. A. sclateri could therefore be regarded as an indicator species in the context of instream flow requirements for the Senqunyane River below the proposed Mohale Dam wall.

Ferreira, M., Dr.; Van Vuren, J.H.J., Prof. / The Wilge River is one of many adjoining tributaries of the Olifants River located in the Olifants Water Management Area (WMA4) within the Highveld (11) – Lower Level 1 Ecoregion (Dallas, 2007). These river systems experience extreme demand for natural resources, as they flow through heavily utilised economic hubs. They are closely associated with land modification and pollution, primarily mining and industrial-related disturbances and extensive agricultural activities, all of which are the primary cause of impairment to river health. The primary aim of this study was to study the aquatic macroinvertebrate communities at six monitoring sites along the Wilge River, coupled with two monitoring sites on adjoining tributaries, and to further identify the driving variables that influence these communities both spatially and temporally. Functional Feeding Groups (FFGs) of the aquatic macroinvertebrates and the surrounding land use in the project area was taken into account. The analysis of in situ water quality measured during the period March 2010 to May 2013, clearly illustrated high levels of variation both spatially and temporally. In situ water quality was a limiting factor to the aquatic ecosystem from a Dissolved Oxygen (DO) and Percentage Saturation (DO%) perspective. The remaining parameters were within the South African guideline for aquatic ecosystems (DWAF, 1996). Habitat availability illustrated clear seasonal variation as well, of which the wet season indicated better habitat availability compared to the dry season. The dominant biotopes in the study area were vegetation (VEG) and gravel, sand and mud (GSM). Site WIL04 illustrated the poorest habitat integrity overall primarily attributed to the site’s steep incised banks and deep channel which lacks the stones biotope. The South African Scoring System, Version 5 (SASS5) results indicated that there was a change in the integrity of the aquatic macroinvertebrate community’s in the study area and further illustrated variability both spatially and temporally. It was evident that the aquatic macroinvertebrate communities within the Wilge River and two adjoining tributaries sampled, were generally in a slightly to modified state with moderate variations. The lowest number of taxa, SASS5 and average score per taxon (ASPT) values was recorded at site WIL04 and this was mainly brought about due to changes in flow and habitat availability. The ASPT score ranged from 3.8 at site WIL04 to 7.7 at site WIL02, indicating that the aquatic macroinvertebrate communities were primarily composed of tolerant and moderately tolerant taxa. Of these mostly tolerant taxa, predators and gathering collector populations were the most dominant FFG, with the shredders being the least abundant within the study area. The Bray-Curtis cluster analysis of the aquatic macroinvertebrate communities clearly illustrated a high level of similarity and seasonal variation among the communities. The high similarity was an indication that similar taxa occurred at the sites within the groups identified. However, in accordance with the Similarity Percentages (SIMPER) analysis, there was no clear indication of dominant taxa. There was however a separation of sites TRI01 and WIL04. This was expected due to differences in the physical stream condition (flow) and other habitats / general biotopes, primarily at site WIL04. Stream bed composition is one of the most important physical factors controlling the structure of freshwater invertebrate communities (Mackay and Eastburn, 1990). The separation and similarity of these two sites were not a consequence of dominant taxa, but rather a consequence of differing water quality, habitat availability and common tolerant taxa driving the system. Inclusive, the seasonal variation illustrated was contributing to the changes in the in situ water quality and habitat availability, thus making seasonal variation also a driving variable, in the differences between the sites. The Redundancy Analysis (RDA) bi-plots indicated, as with the Bray-Curtis similarity matrices and related NMDS plot, that there was a distinct seasonal separation. It further illustrated a clear separation of site TRI01 and WIL04 due to reasons mentioned above. All the environmental variables, with the exception of pH, was identified as significant drivers in the river systems (p<0.05). This however varied seasonally. During the wet season, clarity, DO and pH were the significant drivers, while clarity, TDS/EC, percentage saturation and pH were the significant drivers during the dry season (p<0.05). These drivers were expected due to possible sources namely intensive agriculture in the project area. The RDA tri-plots further indicated the significant role that the ASPT, SASS5 score and the IHAS played within the aquatic macroinvertebrate community (p<0.05). This confirms the importance of habitat as a driving variable in aquatic macroinvertebrate community structures. Consequently, the driving variables in the separation of the sites along the Wilge River and two adjoining tributaries, appear to be a combination of variables (DO, percentage saturation, TDS/EC, clarity and pH), including habitat availability (based on IHAS scores). To determine the effects and relations between the primary driving changes, to the surrounding land uses in the project area, further multivariate analyses were conducted, which included the FFGs. It was clearly indicated that predators have a negative correlation with the rest of the FFG’s which was expected. As the percentage of predators increase at a site, the percentage of the other FFG’s decreased. Therefore, there was a large variation and clear changes in the food sources constantly entering into the river system. This is normally related to changes in the land use.

Ph.D. / The primary objective of the study was to determine the ecological integrity of the Klip River. The protocols applied during the study gave a reliable and good reflection of the overall ecological integrity, as well as the state of different components determining the overall integrity. The ecological integrity of the most recent assessment (February 1999) is summarized in Figure 8.2. It was decided to keep the different components determining ecological integrity (physico-chemical, physical, biological) separate and not to combine everything into one score. When expressed separate, such as in the case of Figure 8.2, it is possible to observed deterioration in overall ecological integrity at a site, and it is also evident which of the components are responsible for the degradation. As mentioned previously, biological communities, and thus biotic integrity, are the best indicators of overall ecological integrity, due to the fact that they integrate both water and habitat related stresses over time. Habitat and water quality assessments are indications of the conditions prevailing at the time of sampling, while biota give an indication of the conditions prevailing over the long term. Invertebrates have shorter life cycles, and in many cases have a terrestrial phase, therefore they recolonise quicker than fish may be able to do after a pollution incident. Invertebrates can therefore be seen as indicators of short-term biological integrity, while fish indicate long-term biological integrity of a river. / Prof. G.J. Steyn

MSc. (Zoology) / The Albasini Dam was used as a reference site outside the DDT (1, 1, 1-trichloro-2, 2-bis (p-chlorophenyl) ethane) - sprayed area in a previous survey conducted from 2006 to 2008. DDT, endocrine disrupting chemicals and inorganic chemicals were detected in the dam. A histological analysis of fish from the dam showed histological alterations in heart, liver, gills, and gonads. Therefore, it was necessary to follow up the health status of the dam by monitoring the levels of organic and inorganic chemicals and their effects on fish. The aim of the present study was to determine the health status of three freshwater fish species, Clarias gariepinus, Oreochromis mossambicus, and Coptodon (Tilapia) rendalli from the Albasini Dam, using fish histology as a biomonitoring tool. In total, 18 fish were sampled using gill nets; these included Clarias gariepinus (n=5); Coptodon (Tilapia) rendalli (n=4) and Oreochromis mossambicus (n=9). The histology-based fish health assessment included a standard fish necropsy; a calculation of blood parameters (haematocrit, leukocrit and total plasma protein); somatic indices and the condition factor and a qualitative and semi-quantitative histological assessment of five target organs: liver, heart, gills, kidney and gonads. Water, sediment and fish muscles samples were collected and analysed for inorganic chemicals and organic chemicals. Inorganic chemicals were analysed by means of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Optic Emission Spectrometry (ICP-OES). Organic chemicals in water and fish muscles were analysed using Gas Chromatography-Mass Spectrometry (GC-MS). Nutrients and physical parameters of water were also measured...

This thesis examines the extent and intensity of the effects of impoundments on selected physical, chemical and biotic conditions in an impounded southern African river. Life-history characteristics and environmental requirements which determine the success of impoundment-outlet blackflies in southern Africa were studied. Difficulties with the identification of immature blackflies led to a search for additional diagnostic characters, the description of larvae of seven species previously unknown, and the development of new keys to the species of Simulium (larvae and pupae) in southern Africa. Distribution records for each species are presented, and their ecology is summarised. Three pairs of closely related species, which were formerly indistinguishable, can now be recognised by differences between the structure of their cephalic fan microtrichia. Monthly physical, chemical and invertebrate samples at 16 sites upstream and downstream of four impoundments in the Buffalo River, eastern Cape, were taken over a period of two years. The downstream effects of impoundments on these parameters depended on the variable examined, the position of the impoundment along the river profile, the depth from which water was released, and the quality of the inflowing water. Impoundments in the Buffalo River caused an upstream shift of the thermal and suspended organic conditions, and the distribution of blackfly species. Surface-release impoundments in the clean, upper-reaches of the river caused increases in water temperature (by as much as 8ºC) and chlorophyll a (by as much as 600%). Recovery to riverine conditions was within 2.6 to 18.4 km, depending on flow. A polluted, surface-release impoundment in the middle-reaches of the river had a slight dampening effect on river temperatures, converted the particle size spectrum of the river from small (<80 μm) to large (250-1000 μm), and improved the water quality of the downstream reaches (with the exception of nitrate concentrations, which were higher in the tailwaters compared to inflowing water). An impoundment in the lower reaches caused reductions in maximum temperature of up to 6ºC when releasing water from the surface, and up to 16ºC when releasing water from the bottom. Bottom-released water carried high concentrations (36 to 190 g m³) of small (<5 μm) and largely inorganic (86 to 93%) material.Twenty species of blackflies were found in the Buffalo River, of which 18 were distinguishable as larvae. They were divided into those which were widespread (5 taxa), those restricted to waterfalls and mountain torrents (2 taxa), those found in the foothill stony run zone (6 taxa), and rare taxa (5 taxa). Impoundments in the Buffalo River did not alter population densities of blackfly larvae, but did alter blackfly species composition, favouring five species commonly found in mid-order streams in southern Africa (s. meduseaforme, S. hargreavesi, S. nigritarse, S. adersi and s. damnosum s.l.) at the expense of upper-reach species (s. rutherfoordi, S. letabum and s. impukane). These five species are regarded as typical of impoundment-outlets, and were small, multivoltine flies whose larvae shared a generalised cephalic fan microtrichial structure, consisting of a single row of moderately differentiated microtrichia. A strong relation was found between cephalic fan microtrichial structure and larval habitats: Taxa found in fast-flowing, clear water had a more complex fan structure compared to those found in slow-flowing, turbid water. It is concluded that impoundment-induced changes to hydrodynamics and transported material (food) are important factors which have changed the distribution of blackflies in southern Africa in recent times. These changes are more severe downstream of upper-reach impoundments than middle or lower-reach impoundments.

North American prairie headwater streams are highly threatened and relatively poorly studied. Most studies on prairie streams have occurred at the Konza Prairie Biological Station, a tallgrass prairie Long Term Ecological Research site in the Flint Hills ecoregion near Manhattan, KS. According to the Stream Biome Gradient Concept, several ecosystem factors vary along a gradient from more allochthonous forested streams to more autochthonous desert streams, with grassland streams often intermediate in several key ecological factors including litter inputs, primary production, and invertebrate abundance and biomass. However, few studies have examined the degree of variation that exists within prairie headwater streams, and whether this variation occurs along a longitudinal gradient as well, with more mesic tallgrass prairie streams differing from more xeric shortgrass prairie streams, and mixed-grass sites intermediate between the two. I examined thirteen prairie headwater stream sites in the central United States from 2014 to 2017. My objective was to determine whether basal resource composition – including standing stocks of coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and very fine particulate organic matter (VFPOM), sestonic and benthic chlorophyll-a levels, and sources of CPOM – differed significantly among streams in tallgrass, mixed-grass, and shortgrass prairie regions. In addition, I examined whether invertebrate communities differed among tallgrass, mixed-grass, and shortgrass prairie regions, and whether this was reflected in the functional feeding group composition, habit composition, voltinism, and dispersal ability of invertebrate communities. There were no significant differences in total CPOM, FPOM, and VFPOM standing stocks among regions. However, CPOM composition did differ with region, with tallgrass sites having higher standing stocks of leaf litter, but lower standing stocks of grass litter and macrophyte litter than the other regions. Benthic chlorophyll-a did not differ significantly among regions, but there were lower sestonic chlorophyll-a levels in tallgrass sites. Given higher light availability and nutrient levels in shortgrass and mixed-grass streams, lack of stable substrata may be limiting benthic algae in these regions. Invertebrate abundance and biomass were highest in mixed-grass sites and lowest in tallgrass sites, with shortgrass sites intermediate. Mixed-grass sites also had significantly higher Shannon diversity and taxa richness than tallgrass sites. A NMDS revealed that sites differed in overall community structure. Functional feeding group composition did not differ significantly across regions, with collector-gatherers, followed by predators, dominating in all sites. High Predator-Prey Index (predator biomass: other invertebrate biomass) values in each region indicates strong top-down pressure and high turnover rates of prey taxa. While there was a weak correlation between leaf litter AFDM and invertebrate community structure, the correlation between latitude and longitude and invertebrate community structure was much higher, indicating that basal resources may not be the main drivers in these systems. Invertebrate habit composition did not differ with region; all regions were dominated by taxa preferring fine substrata (burrowers and sprawlers). All regions showed selection against semivoltine invertebrates and were dominated by high dispersing insect taxa, though the proportion of the insect community that consisted of high dispersers did not differ significantly with region. My results suggest that generalizing about prairie streams based on studies from one or a handful of sites may not be prudent, at least for some aspects. The higher proportion of autochthonous inputs in shortgrass and mixed-grass regions may drive increased invertebrate abundance, biomass, richness, and diversity, but the relative hydrologic stability of the mixed-grass sites might also explain these results or have an interactive or additive relationship with primary production. Overall, the link between basal resources and communities across prairie types was somewhat weak, and all regions were dominated by collector-gatherers with rapid life-cycles and high dispersal abilities, indicating that disturbance may be a more important community filter than basal resource composition. Streams in all three regions have highly variable hydrology, and this may be an overriding factor that results in similarity in communities.

No description available.

Invasions from coho salmon were first reported in the Cape Horn Biosphere Reserve (CHBR) in 2019 which is the most southern distribution registered to date. The CHBR is known for its high number of endemic species and unique biodiversity, such as the native fishes Galaxias maculatus and Aplochiton taeniatus. There are now three invasive salmonid species in the rivers of CHBR and are a potential threat to the native fish taxa. Stable isotope and gut content analysis were used to understand resource utilization by both native galaxiid and invasive salmonid taxa, as well as aquatic macroinvertebrates and riparian spiders. The natural laboratory study approach applied to this research, allowed for comparisons of differences within streams that contain conditions in which fish do not occur naturally, to sites in which high densities of invasive salmonid exist. Analysis of the trophic niche and diet in this study showed the importance of marine resource use by the native galaxiid and coho salmon juveniles supported with elevated δ15N and δ34S ratios. Diet analysis also confirmed there was the highest similarity between the coho salmon juveniles and the native fish. Altered behavior and habitat use was shown through the isotope and diet analysis for the galaxiid in snow melt streams which could be due to the high density of invasive salmonids in these streams. The invasive salmonids were found to impact aquatic macroinvertebrate populations, specifically larger bodied Trichoptera abundance. Aquatic insect emergence was negatively correlated to salmonid densities. The aquatic insect emergence revealed alterations with significantly higher biomass of aquatic insect emergence in upstream sites without invasive fish. Lastly, aquatic insect predator (Hydrobiosidae: Rheochorema sp.) exhibited a suppressed trophic position in rivers with invasive salmonids. An unexpected finding from the study was the refugium stream habitat conditions that has been shown to be important for conserving the native fish in the CHBR. We conclude that the impacts from invasive species are significant enough to disrupt lower trophic levels especially aquatic insects. The altered aquatic emergence and insect behavior have the potential to disrupt food webs and ecosystem functioning in the southernmost protected ecoregion in the world.

No description available.